The invention relates to a hydraulic system for a motor vehicle transmission.
A hydraulic system for a motor vehicle transmission, with a plurality of gear-selection pressure chambers, which are provided for the selection of a plurality of transmission gears, is already known from EP 1 420 185 A2.
A hydraulic system which has 5 double-acting cylinders with 10 gear-selection pressure chambers is known from DE 10 2005 058 779 A1. However, in that document the supply of switching pressure to the 5 cylinders as well as the control of the hydraulic system is provided in a costly manner.
The object of the invention is, in particular, to simplify the hydraulic system and to improve the controllability.
The hydraulic system for a motor vehicle transmission has at least ten gear-selection pressure chambers, which are provided for the selection of a plurality of transmission gears; it also has at least two actuation valves, each of which is provided for setting at least one actuation pressure for the gear-selection pressure chambers; it also has at least one first selection valve unit, at least one second selection valve unit, and at least one third selection valve unit, which are provided for connecting the actuation valves to the gear-selection pressure chambers.
According to the invention the second selection valve unit is directly connected to four gear-selection pressure chambers in order to transmit actuation pressure and the third selection valve unit is directly connected to 6 other gear-selection pressure chambers and directly to the second selection valve unit in order to transmit actuation pressure.
In this way, only two selection valve units are directly connected to 10 gear-selection pressure chambers, so that an efficient and cost-effective hydraulic system design is produced.
An advantageous further embodiment of the invention is characterized in that the third selection valve unit has a first and a second selection valve, wherein the second selection valve hydraulically connects the first selection valve unit as required to two of the gear-selection pressure chambers or to the second selection valve unit.
In a further advantageous modification, a hydraulic system for a motor vehicle transmission is proposed, with at least ten gear-selection pressure chambers which are provided for the selection of a plurality of transmission gears, with at least two actuation valves, each of which is provided for setting at least one actuation pressure for the gear-selection pressure chambers, with at least one first selection valve unit, at least one second selection valve unit, and at least one third selection valve unit, which are provided for connecting the actuation valves to the gear-selection pressure chambers, wherein at least the first selection valve unit and the second selection valve unit have different switching pressure thresholds, as well as with at least one first control valve, which is connected in control terms at least to the first selection valve unit and the second selection valve unit and which is provided in order to set at least two control pressures which are different from one another for at least partially separate selection of the first selection valve unit and the second selection valve unit, and with at least one second control valve, which is connected in control terms at least to the third selection valve unit and which is provided in order to set at least one control pressure for switching of the third selection valve unit. Due to such a configuration of the hydraulic system, with a particularly low number of valves a particularly high number of transmission gears can be switched, so that a particularly compact, lightweight and/or cost-effective hydraulic system can be provided for selection of a high number of transmission gears. In particular, a particularly compact, lightweight and/or cost-effective hydraulic system can be provided, by means of which more than seven forward transmission gears can be switched. In this way, the hydraulic system can be improved, in particular, with regard to a number of switchable transmission gears to save on installation space, weight and/or costs.
The selection valve units are preferably provided in order to guide the actuation pressure set by at least one of the actuation valves to the corresponding gear-selection pressure chamber. The selection valve units preferably only have purely hydraulic switching sliders. A “selection valve unit” should be understood in particular to mean a unit which has at least one selection valve, wherein the unit can also have a plurality of selection valves for reasons of production and/or installation space. If a selection valve unit has only one selection valve, this selection valve unit is preferably formed by the selection valve. If a selection valve unit has a plurality of, in particular two, selection valves, this selection valve unit is preferably formed by the plurality of, in particular by the two selection valves, wherein it is conceivable in principle to represent the function of the plurality of, in particular, the two selection valves by one single selection valve. Advantageously, the first selection valve unit only has one single selection valve, the second selection valve unit only has one single selection valve and the third selection valve unit only has two selection valves. A “switching pressure threshold” should in particular be understood to mean a control pressure threshold of a valve or a valve unit so that, at a control pressure above the control pressure threshold, the valve or the valve unit is switched in its switching position and at a control pressure below the control pressure threshold the valve or the valve unit is switched in its normal position. The switching pressure threshold is preferably defined or set by at least one spring and/or by at least one control pressure surface, on which the control pressure acts, of the corresponding valve or the corresponding valve unit. The control pressure set by the first control valve preferably acts simultaneously as control pressure for the first selection valve unit and as control pressure for the second selection valve unit. A “normal position” should be understood in particular as a valve position of a valve or a valve unit, which position is adopted by the valve or the valve unit without application of a control pressure, so that the valve preferably also adopts the normal position when the internal combustion engine of the motor vehicle having the motor vehicle transmission is stationary. The actuation valves and/or the control valves are preferably electrical controllable. “Provided” should be understood in particular to mean specially constructed, designed, equipped and/or arranged.
Furthermore, it is proposed that the first selection valve unit is provided in order to connect both actuation valves to the third selection valve unit, so that already a transmission of the actuation pressure to the third selection valve unit between at least two connecting paths can be distinguished. The actuation valves can preferably be connected only via the first selection valve unit to the third selection valve unit. Advantageously the actuation pressure set by the actuation valves can be directed only via the first selection valve unit to the third selection valve unit.
Furthermore, it is proposed that the third selection valve unit is provided in order to connect the first actuation valve unit to the second selection valve unit, so that without an additional valve the number of selectable connection paths for the actuation pressure set by the actuation valves can be increased. The first selection valve unit can preferably be connected only via the third selection valve unit to the second selection valve unit. Advantageously the actuation pressure transmitted by the first selection valve unit can be directed only via the third selection valve unit to the second selection valve unit.
In particular, it is advantageous if the third selection valve unit is provided in order to connect the first selection valve unit to at least one of the gear-selection pressure chambers, so that the actuation valves can be connected to the gear-selection pressure chambers according to the transmission gear to be switched. The first selection valve unit is preferably provided in order to connect the first selection valve unit to at least one gear-selection pressure chamber and to the second selection valve unit. The second selection valve unit and the third selection valve unit are preferably arranged in flow terms between the gear-selection pressure chambers and the first selection valve unit. The second selection valve unit is preferably provided in order to transmit the actuation pressure transmitted by the first selection valve unit and the third selection valve unit to at least one of the gear-selection pressure chambers. The actuation pressure transmitted by the first selection valve unit can either be directed via the third selection valve unit to at least one gear-selection pressure chamber or can be directed via the third selection valve unit and the second selection valve unit to at least one gear-selection pressure chamber. The second selection valve unit and the third selection valve unit are preferably provided in order to transmit the actuation pressure transmitted by the first selection valve unit to the corresponding gear-selection pressure chamber. The second selection valve unit is preferably provided in order to supply four of the gear-selection pressure chambers with the actuation pressure transmitted by the first selection valve unit and the third selection valve unit. The third selection valve unit is preferably provided in order to supply six of the gear-selection pressure chambers with the actuation pressure transmitted by the first selection valve unit.
Furthermore, it is advantageous if the switching pressure threshold of the second selection valve unit is greater than the switching pressure threshold of the first selection valve unit, so that an advantageous state can be produced in which the first selection valve unit is switched in its switching position and the second selection valve unit is switched in its normal position.
In an advantageous design the hydraulic system has at least one further valve with a switching pressure threshold which differs from the third selection valve unit, wherein the second control valve is connected in control terms to the at least one further valve and is provided in order to set at least two control pressures which are different from one another for at least partially separate switching of the third selection valve unit and the further valve. As a result, the second control valve can be used additionally for controlling the third selection valve unit for controlling the at least one further valve, so that at least one further unit of the hydraulic system can be actuated in particular to save on weight, installation space and/or costs. The control pressure set by the second control valve preferably acts simultaneously as control pressure for the third selection valve unit and as control pressure for the at least one further valve. The two control valves are advantageously provided in each case to control two valves, in particular as they are each provided in order to set two different control pressures.
Furthermore, it is proposed that the switching pressure threshold of the further valve is greater than the switching pressure threshold of the third selection valve unit, so that an advantageous state can be produced in which the third selection valve unit is switched in its switching position and the second selection valve unit is switched in its normal position.
Furthermore, it is proposed that the further valve is provided for controlling a parking lock, so that by means of the three selection valve units and the two control valves an actuation pressure supply of the at least ten gear-selection pressure chambers and actuation of the parking brake can be controlled.
In particular, it is advantageous if the hydraulic system has at least five double-acting gear selectors, which each have two of the gear-selection pressure chambers, so that the hydraulic system can be further improved with regard to its installation space requirement, its weight and/or its costs. A “double-acting gear selector” should be understood in particular to be a gear selector which has an actuating cylinder and an actuating piston arranged displaceably in the actuating cylinder, wherein the actuating cylinder and the actuating piston enclose two gear-selection pressure chambers acting in opposite directions, so that the actuating piston can be moved in a first switching direction by an actuation pressure in the first gear-selection pressure chamber and can be moved in a second switching direction by an actuation pressure in the second gear-selection pressure chamber. The selection valve units are advantageously provided in order to connect the first actuation valve in each case to one of the two gear-selection pressure chambers of the double-acting gear selectors and to connect the second actuation valve in each case to the other one of the two gear-selection pressure chambers of the double-acting gear selectors.
Furthermore, it is advantageous if the gear-selection pressure chambers are divided into first gear-selection pressure chambers of the gear selectors and into second gear-selection pressure chambers of the gear selectors and the selection valve units are provided in order to connect the first actuation valve to the first gear-selection pressure chambers and to connect the second actuation valve to the second gear-selection pressure chambers. In this way, the control of the actuation pressure supply of the ten gear-selection pressure chambers can be simplified.
Further advantages can be seen from the following description of the drawings. An exemplary embodiment of the invention is shown in the drawings. The drawings, the description of the drawings and the claims contain numerous features in combination. The person skilled in the art will also advantageously consider the features individually and will combine them to form further meaningful combinations.